Deepwater Horizon Explosion

Note: This post summarizes the incident occurred one month ago. The context is partially modified from Deepwater Horizon and some other relative terms on wikipedia.org.

On April 20, 2010, an explosion occurred on Deepwater Horizon, an offshore rig owned by Transocean and leased by BP, and it caught fire.[1] Two days later, it sank in water approximately 5,000 feet (1,500 m) deep, and has been located resting on the seafloor approximately 1,300 feet (400 m) northwest of the well .[2]

INTRODUCTION

Deepwater Horizon is a Reading & Bates Falcon RBS8D design, Hyundai Heavy Industries build, 5th generation deepwater semi-submersible drilling unit capable of operating in harsh environments and water depths up to 8,000 ft (upgradeable to 10,000 ft) using 18¾in 15,000 psi BOP and 21in OD marine riser.[3] Construction started in December 1998 and it was delivered in February 2001 after the acquisition of R&B Falcon by Transocean. Since arriving in the Gulf of Mexico, Deepwater Horizon was under contract to BP Exploration. Its work included wells in the Atlantis and Thunder Horse fields, a 2006 discovery in the Kaskida field [4] and the 2009 Tiber oilfield.[5] In 2002, the rig was upgraded with “e-drill”, a drill monitoring system where technicians based in Houston, Texas receive real-time drilling data from the rig and transmit maintenance and troubleshooting information.[6] On September 2, 2009, the giant offshore rig drilled on the Tiber oilfield the deepest oil and gas well ever drilled with a true vertical depth (TVD) of 35,050 feet (10,680 m) and measured depth (MD) of 35,055 feet (10,685 m), of which 4,132 feet (1,259 m) was water.[7] In October 2009 BP extended the contract for Deepwater Horizon by three years, to begin in September 2010.[8] The lease contract was worth $544 million, a rate of $496,800 per day.[9]

Fig. 1 Deepwater Horizon Offshore Rig

BACKGROUND

Before the accident, it worked on BP’s Mississippi Canyon Block 252, referred to as the Macondo prospect.[10] The rig caught an explosion when it was last located approximately 41 miles offshore Louisiana on Mississippi Canyon block 252. [11]

Fig. 2 Location of Deepwater Horizon [12]

EXPLOSION

Though the cause of the explosion on the Deepwater Horizon remains under investigation, officials with Transocean have said a blowout within the deep oil well was likely to blame for the deadly blast. At the time of the accident, half of the crews were cementing, and the other half were installing casing to secure the walls of the well. [13] It was the rig in the final phases of drilling a well in which casing is cemented in place, reinforcing the well. This is a delicate process as there is the possibility of a blowout, the uncontrolled release of formation fluids from the well. [14]

The fire reportedly started at approximately 10 PM CST on Apr. 21, 2010. [11] Adrian Rose, a vice president for Transocean Ltd., said that there was “no indication of any problems” as crew members carried out routine work around the drill site before the blast. Officials said 126 people were on board at the time of the explosion. Of the 115 accounted-for workers, 17 injured were evacuated by helicopter from the rig, and another 94 people were taken to shore with no major injuries, and four more were transferred to another vessel, according to the Coast Guard. The rest of 11 were missing. [15]

Fig. 3 Deepwater Horizon was on fire[16]

Fig. 4 Deepwater Horizon was on fire[16]

According to survivors words, the sudden explosion gave them less than five minutes to escape as the alarm went off, and Chad Murray, 34, the rig’s chief electrician said he didn’t think any of the missing could have survived. [17]

The United States Coast Guard (USCG) launched a massive rescue operation.[11] One day after the explosion USCG spokesman Mike O’Berry said four helicopters, four Coast Guard boats and a plane were helping search for the missing workers. [18] Two USCG cutters continued the search overnight. By 6 AM of Apr 22, USCG has surveyed 1,940 square miles in a series of 17 separate air and sea search missions since the Tuesday explosion. [19] Official confirmed Murray’s word on Thursday and USCG stopped the search for the 11 missing persons. [20]

Fig. 5 United States Coast Guard Rescued the Wounded[19]

After the blast, the rig was tilting as much as 10 degrees. [21] Fire boats sprayed the rig with water in an unsuccessful bid to douse the flames. After burning for more than a day, Deepwater Horizon sank in water approximately 5,000 feet (1,500 m) deep, and has been located resting on the seafloor approximately 1,300 feet (400 m) northwest of the well on April 22, 2010. [2]

On the day Deepwater Horizon sank on the bottom of Gulf of Mexico, the USCG and the Minerals Management Service launched an investigation on possible causes of the explosion. [22] According to interviews with rig workers conducted during BP’s internal investigation, a bubble of methane gas escaped from the well and shot up the drill column, expanding quickly as it burst through several seals and barriers before exploding.[23] The blowout preventer (BOP, a huge and complex tower of valves and pipe crimpers on the ocean floor designed to shut down a well in an emergency) was supposed to activate once the escaping gas was detected and the alarm went off, but unfortunately it didn’t work. Bob Fryar, senior vice president of BP’s exploration and production operations in Angola, in southwestern Africa said BP had found there were some leaks on the hydraulic controls on the BOP, though it is unclear whether it caused the malfunction. [24]

AFTERMATH

Shortly after the explosion, the concern about the crude oil spill from the incident on the environment became more and more serious because the failure of BOP caused the oil leakage from the borehole.[25] Since BP has taken several measures (1. A remotely operated underwater vehicle attempting to turn on the Deepwater Horizon blowout preventer;[26] 2. BP now aims to deploy a small “top hat” dome over the leak after its effort over the weekend to cover it with a huge metal box was stymied by a buildup of crystallized gas hydrates;[27] 3. After several attempts, BP successfully inserted a 6 inches wide tube into a jagged 21 inches pipe that is leaking oil onto the Gulf seabed, which is surrounded by a rubber seal and attached to a tanker at the surface.[28]) to stop the oil leakage from the borehole, the spill is expected to eclipse the 1989 Exxon Valdez oil spill as the worst US oil disaster in history.[29] BP is leading the clean-up work of oil spill, and working with US government, communities, and organizations. [30]

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3 Responses to Deepwater Horizon Explosion

While watching the latest news about the BP Oil spill, a frightening thought came to mind: what if we can’t stop the oil? I mean, what happens if after all the measures to cap the pipe fail, (i.e., “Top Hat”, “Small Hat” and “Top Kill”). What then? An accident this problematic is new territory for BP. The oil pipeline is nearly a mile down on the ocean floor, accessible only by robots. Add on top of that the extreme pressure at which the oil is flowing out of the pipeline and there you have it: the perfect storm.

Moreover, scientists also claim that they’ve found an enormous plume of oil floating just under the surface of the ocean measuring approximately 10 miles long, 3 miles wide and 300 feet thick. (I’m no math genius, but I bet one of you reading this could figure out just how many barrels of oil that is…)

There are new estimates that the amount of oil spewing into the Gulf of Mexico is anywhere from 50,000 to 100,000 barrels of oil a day: that’s a far cry from BP’s estimated 5,000 barrels a day. If BP’s estimates are correct, the total amount of oil now in the Gulf would be approximately 150,000 barrels (or 6,300,000 gallons). That’s barely enough to fill 286 swimming pools: sixteen feet, by thirty-two feet, by eight and a half feet deep. That wouldn’t cover an area the size of New York City, let alone an area the size of Delaware. Obviously, the spill is much larger than we are being led to believe. If the leak can’t be stopped, in a year’s time, we’ll have roughly 18,250,000 barrels of oil (or 766,500,000 gallons) in our oceans, killing our marine and animal wildlife. Such a calamity would be environmentally and economically disastrous. I’m not a religious man, but I pray that BP and our government work fast to end this catastrophe.

Glad to hear from you, the destructionist. I am happy to give you answers to your concerns, since I am not so familiar with BP.
1. Eventually the well could be shut down, I believe. As for engineering, it is not only reach the target but economically. As we know, BP has tried a lot of methods to reduce the oil leakage which I have mentioned in my previous post. Else you can find more information in details as “Engineers work to place siphon tube at oil spill site“. It is obviously that BP tried the easiest and least cost one at first. If all the listed methods failed, BP could shut down the well eventually. I totally understand your concerns about if all the measures to cap the pipe failed. Yes, it is possible. But BP could tried more than once to kill the well. Finally, I believe it works.
2. The plume of oil contains not only crude oil but also reservoir fluids and sea water. Definitely it is a disaster for gulf of Mexico, we still need to evaluate the damage in a rational way.
3. Finally, I need tell you some basic stuff about oil reservoir. The oil is stored in the pores of the rocks underground. If there is pressure drop over the rock, the oil moves. Usually with oil producing, the reservoir pressure drops. Then, the oil flow rate goes down. That is why the oil well has a life. Thus, the oil won’t leak always.

Hopefully these words can give you some idea about the severe oil spill.